Add APIs for BHInvocation:

methodSignature
getReturnValue:
setReturnValue:
getArgument:atIndex:
setArgument:atIndex:

BlockHook.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
 s.name         = "BlockHook"
-s.version      = "1.5.3"
+s.version      = "1.5.4"
 s.summary      = "Hook Objective-C blocks."
 s.description  = <<-DESC
 Hook Objective-C blocks with libffi. It's a powerful AOP tool for blocks. BlockHook can run your code before/instead/after invoking a block. BlockHook can even notify you when a block dealloc. You can trace the whole lifecycle of a block using BlockHook!

BlockHook/BlockHook.h

@@ -29,12 +29,12 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  Arguments of invoking the block. Need type casting.
  */
-@property (nonatomic, readonly) void *_Nullable *_Null_unspecified args;
+@property (nonatomic, readonly) void *_Nullable *_Null_unspecified args DEPRECATED_MSG_ATTRIBUTE("Use getArgument:atIndex: or setArgument:atIndex: instead");
 
 /**
  Return value of invoking the block. Need type casting.
  */
-@property (nonatomic, nullable, readonly) void *retValue;
+@property (nonatomic, nullable, readonly) void *retValue DEPRECATED_MSG_ATTRIBUTE("Use getReturnValue: or setReturnValue: instead");
 
 /**
  Mode you want to insert your custom logic: Before, Instead, After OR Dead.
@@ -62,10 +62,36 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)retainArguments;
 
+/**
+ Gets the receiver's return value.
+ If the NSInvocation object has never been invoked, the result of this method is undefined.
+
+ @param retLoc An untyped buffer into which the receiver copies its return value. It should be large enough to accommodate the value. See the discussion in NSInvocation for more information about buffer.
+ */
 - (void)getReturnValue:(void *)retLoc;
+
+/**
+ Sets the receiver’s return value.
+
+ @param retLoc An untyped buffer whose contents are copied as the receiver's return value.
+ @discussion This value is normally set when you send an invokeOriginalBlock message.
+ */
 - (void)setReturnValue:(void *)retLoc;
 
+/**
+ Sets an argument of the receiver.
+
+ @param argumentLocation An untyped buffer containing an argument to be assigned to the receiver. See the discussion in NSInvocation relating to argument values that are objects.
+ @param idx An integer specifying the index of the argument. Indices 0 indicates self, use indices 1 and greater for the arguments normally passed in an invocation.
+ */
 - (void)getArgument:(void *)argumentLocation atIndex:(NSInteger)idx;
+
+/**
+ Sets an argument of the receiver.
+
+ @param argumentLocation An untyped buffer containing an argument to be assigned to the receiver. See the discussion in NSInvocation relating to argument values that are objects.
+ @param idx An integer specifying the index of the argument. Indices 0 indicates self, use indices 1 and greater for the arguments normally passed in an invocation.
+ */
 - (void)setArgument:(void *)argumentLocation atIndex:(NSInteger)idx;
 
 @end

BlockHook/BlockHook.m

@@ -242,6 +242,7 @@ @interface BHInvocation ()
 @property (nonatomic, readwrite) BlockHookMode mode;
 @property (nonatomic) NSMutableData *dataArgs;
 @property (nonatomic) NSMutableData *dataRet;
+@property (nonatomic) NSMutableDictionary *mallocMap;
 @property (nonatomic) NSMutableDictionary *retainMap;
 @property (nonatomic, getter=isArgumentsRetained, readwrite) BOOL argumentsRetained;
 @property (nonatomic) dispatch_queue_t argumentsRetainedQueue;
@@ -291,14 +292,6 @@ - (void)setArgumentsRetained:(BOOL)argumentsRetained
 - (void)invokeOriginalBlock
 {
     [self.token invokeOriginalBlockWithArgs:self.realArgs retValue:self.realRetValue];
-    if (self.isArgumentsRetained) {
-        for (NSUInteger idx = 0; idx < self.numberOfRealArgs; idx++) {
-            void *argBuf = self.realArgs[idx];
-            if (argBuf != NULL) {
-                free(argBuf);
-            }
-        }
-    }
 }
 
 - (NSMethodSignature *)methodSignature
@@ -311,7 +304,8 @@ - (void)retainArguments
     if (!self.isArgumentsRetained) {
         self.dataArgs = [NSMutableData dataWithLength:self.numberOfRealArgs * sizeof(void *)];
         self.retainMap = [NSMutableDictionary dictionaryWithCapacity:self.numberOfRealArgs + 1];
-        void **args = [self.dataArgs mutableBytes];
+        self.mallocMap = [NSMutableDictionary dictionaryWithCapacity:self.numberOfRealArgs + 1];
+        void **args = self.dataArgs.mutableBytes;
         for (NSUInteger idx = 0; idx < self.numberOfRealArgs; idx++) {
             const char *type = NULL;
             if (self.token.hasStret) {
@@ -328,7 +322,9 @@ - (void)retainArguments
 
             NSUInteger argSize;
             NSGetSizeAndAlignment(type, &argSize, NULL);
-            void *argBuf = malloc(argSize);
+            NSMutableData *argData = [NSMutableData dataWithLength:argSize];
+            self.mallocMap[@(idx)] = argData;
+            void *argBuf = argData.mutableBytes;
             memcpy(argBuf, self.realArgs[idx], argSize);
             args[idx] = argBuf;
             [self _retainPointer:args[idx] encode:type key:@(idx)];
@@ -339,10 +335,14 @@ - (void)retainArguments
             self.retValue = *((void **)args[0]);
         }
         else {
+            self.dataRet = [NSMutableData dataWithLength:sizeof(void *)];
+            void *ret = self.dataRet.mutableBytes;
             NSUInteger retSize = self.methodSignature.methodReturnLength;
-            self.dataRet = [NSMutableData dataWithLength:sizeof(retSize)];
-            void *ret = [self.dataRet mutableBytes];
-            memcpy(ret, self.retValue, retSize);
+            NSMutableData *retData = [NSMutableData dataWithLength:retSize];
+            self.mallocMap[@-1] = retData;
+            void *retBuf = retData.mutableBytes;
+            memcpy(retBuf, self.retValue, retSize);
+            ret = retBuf;
             [self _retainPointer:ret encode:self.methodSignature.methodReturnType key:@-1];
             self.args = args;
             self.retValue = ret;
@@ -355,23 +355,31 @@ - (void)retainArguments
 
 - (void)getReturnValue:(void *)retLoc
 {
+    if (!retLoc || !self.retValue) {
+        return;
+    }
     NSUInteger retSize = self.methodSignature.methodReturnLength;
     memcpy(retLoc, self.retValue, retSize);
 }
 
 - (void)setReturnValue:(void *)retLoc
 {
+    if (!retLoc || !self.retValue) {
+        return;
+    }
     NSUInteger retSize = self.methodSignature.methodReturnLength;
-    BOOL result = [self _retainPointer:retLoc encode:self.methodSignature.methodReturnType key:@-1];
-    if (!result) {
-        memcpy(self.retValue, retLoc, retSize);
+    if (self.isArgumentsRetained) {
+        [self _retainPointer:retLoc encode:self.methodSignature.methodReturnType key:@-1];
     }
+    memcpy(self.retValue, retLoc, retSize);
 }
 
 - (void)getArgument:(void *)argumentLocation atIndex:(NSInteger)idx
 {
+    if (!argumentLocation || !self.args || !self.args[idx]) {
+        return;
+    }
     void *arg = self.args[idx];
-    assert(arg);
     const char *type = [self.methodSignature getArgumentTypeAtIndex:idx];
     NSUInteger argSize;
     NSGetSizeAndAlignment(type, &argSize, NULL);
@@ -380,23 +388,25 @@ - (void)getArgument:(void *)argumentLocation atIndex:(NSInteger)idx
 
 - (void)setArgument:(void *)argumentLocation atIndex:(NSInteger)idx
 {
+    if (!argumentLocation || !self.args || !self.args[idx]) {
+        return;
+    }
     void *arg = self.args[idx];
-    assert(arg);
     const char *type = [self.methodSignature getArgumentTypeAtIndex:idx];
     NSUInteger argSize;
     NSGetSizeAndAlignment(type, &argSize, NULL);
-    BOOL result = [self _retainPointer:argumentLocation encode:type key:@(idx)];
-    if (!result) {
-        memcpy(arg, argumentLocation, argSize);
+    if (self.isArgumentsRetained) {
+        [self _retainPointer:argumentLocation encode:type key:@(idx)];
     }
+    memcpy(arg, argumentLocation, argSize);
 }
 
 #pragma mark - Private Helper
 
 - (BOOL)_retainPointer:(void **)pointer encode:(const char *)encode key:(NSNumber *)key
 {
     void *p = *pointer;
-    if (p == NULL) {
+    if (!p) {
         return NO;
     }
     if (encode[0] == '@') {
@@ -413,7 +423,7 @@ - (BOOL)_retainPointer:(void **)pointer encode:(const char *)encode key:(NSNumbe
         char *arg = p;
         NSMutableData *data = [NSMutableData dataWithLength:sizeof(char) * strlen(arg)];
         self.retainMap[key] = data;
-        char *str = [data mutableBytes];
+        char *str = data.mutableBytes;
         strcpy(str, arg);
         *pointer = str;
         return YES;
@@ -585,7 +595,7 @@ - (void *)_allocate:(size_t)howmuch
 {
     NSMutableData *data = [NSMutableData dataWithLength:howmuch];
     [self.allocations addObject:data];
-    return [data mutableBytes];
+    return data.mutableBytes;
 }
 
 - (ffi_type *)_ffiTypeForStructEncode:(const char *)str